© 1999 by European Society of Cardiology
Positive head-up tilt table test in patients with the long QT syndrome
Department of Electrophysiology, and Division of Clinical Research, Instituto Nacional de Cardiologia ‘Ignacio Chávez’ Mexico City, Mexico
AIMS: Syncope in patients with the long QT syndrome is commonly attributed to a ventricular arrhythmia (torsades de pointes). The susceptibility of patients with the long QT syndrome (LQTS) to neurally mediated syncope is currently unknown.
METHODS AND RESULTS: Head-up tilt table testing (70°) was performed in six patients with the long QT syndrome and a history of syncope. All patients had syncope with a mixed response. The RR interval was significantly decreased 2 min before the onset of syncope (980±125 ms vs 630±91 ms, P=0·003), and significantly increased during syncope (983·17±224·71;P=0·006). Non-significant changes in QT intervals were observed. Baseline QT was 513±86 ms and decreased to 450±59 ms 2 min before the onset of syncope (P=0·11). Although not statistically significant, QT intervals during syncope were longer than at 2 min before syncope (485±85 ms vs 450±59 ms;P=0·29).
CONCLUSION: Our results suggest that patients with the LQTS are susceptible to neurally mediated syncope. Whether this susceptibility differs from control populations remains unresolved. From a clinical standpoint, neurocardiogenic syncope should be considered a diagnostic alternative in patients with LQTS.
Key Words: Long QT syndrome, neurally mediated syncope, head-up tilt table testing
Correspondence: Manuel Cárdenas, MD, Chief, Division of Clinical Research, Instituto Nacional de Cardiología ‘Ignacio Chávez’ Juan Badiano # 1 México, DF 14080, Mexico.
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